This invention relates to a combined field box and engine starter for model airplane engines having a bracing assembly that prevents the box from sliding or tipping during an engine starting operation. This invention also relates to a compact, lightweight starter assembly operated by a low-power electric motor and lightweight battery pack.
Although many model airplane engines can be started by flipping the propeller by hand, most modelers start their engines with an electric starter. Prior art electric starters are typically comprised of a relatively large twelve volt electric motor having a receiver cup directly attached to the motor output shaft. The receiver cone or cup is lined with rubber for frictionally engaging the spinner of the model airplane engine. The starter motor is usually powered from a heavy lead-acid or gel-cell twelve volt battery contained in a portable field box.
Field boxes for holding and transporting all of the accessories and equipment needed to start, operate, and maintain model airplanes are also well known in the prior art. Although the size and design of these boxes varies widely, a typical field box is made of plywood and would be about 11/2 to 2 feet long, about 6 inches to a foot wide, and a foot or more high. Such field boxes and their contents may weigh in excess of 30 pounds, including the aforementioned prior art starter in combination with its twelve-volt lead-acid battery, a gallon fuel tank, a manual or electric fuel pump, radio transmitters in the case of radio-controlled model airplanes, and various tools and spare parts. The prior art starter with its large electric motor and lead-acid battery are often the heaviest pieces of equipment, often having a combined weight of between five and ten pounds.
In operation, the modeler first places the model airplane near the field box. With the model airplane resting on the ground, the modeler then grasps the airplane behind the propeller with one hand, and holds the starter in the other hand, which is connected to the twelve volt battery in the field box by way of appropriate wiring. Most such starters include a switch operated by the user which actuates the electric motor when the spinner of the model airplane engine is pressed into the rubber-lined receiving cup. Once the motor is actuated, the rubber-lined cup spins with the output shaft of the electric motor, turning the engine shaft.
While such prior art engine starters and field boxes are generally capable of performing their intended tasks, the applicant has noted a number of shortcoming associated with their use, the most severe of which is safety. When a prior art engine starter is operated in the aforementioned manner, the modeler is in front of the engine and propeller, where he is susceptible to injury if the engine goes to full speed unexpectedly due to, for example, radio malfunction or inadvertent movement of the throttle control. Injuries have also occurred when the modeler has attempted to adjust the engine from such a front position while reaching over the spinning propeller. The awkward squatting or kneeling position that the modeler must assume when starting the engine in this fashion increases the chances of accidental contact with the spinning propeller. In addition to the possibility that the modeler may inadvertently come into contact with the spinning blade, a hard object may sometimes accidently fall into the spinning propeller. Additionally, a propeller may unexpectedly throw a blade. In such cases there is a risk of injury because objects or propeller blades tend to fly forward or outward, where they may strike a modeler kneeling close in front of the airplane. Due to the trend toward larger and more powerful engines (some of which have two horse power or more), and because of the common use of sharp-edged, fiber-reinforced propellers that will not break even after striking a body part, injuries can be severe. Severed fingers, permanent tendon damage, and even life threatening wounds have been sustained by modelers attempting to start engines while kneeling in front of their airplanes.
The lead-acid batteries used in conjunction with such prior art electric starters exacerbate these safety problems. Such batteries require the use of dangerous sulfuric acid and can generate explosive gases. Care must be taken that they are always kept upright and are provided with ventilation. Since they are often sold without electrolyte, the user must go to the trouble of obtaining and adding the potentially dangerous sulfuric acid. While gel-cell batteries may be used instead of lead-acid batteries, these batteries are more expensive and are still about as heavy as lead-acid batteries. Finally, the use of such twelve-volt batteries requires the purchase of a dedicated charger for periodically recharging such batteries.
Still another shortcoming associated with such prior art engine starters is that, despite their great size and weight, many such prior art starters do not have sufficient torque to start the larger internal combustion engines which have recently become popular among modelers. This shortcoming could be partially overcome by using even larger, heavier, and more expensive starters and batteries. But presently, for the largest engines, there are no starters available which generate sufficient torque to start them reliably. Consequently, such large engines can only be started by hand. Finally, the combined weight of such prior art starters and field boxes makes them unwieldy and uncomfortable to carry over even relatively short distances.
Clearly, there is a need for an engine starter which is smaller, lighter, and easier to use than prior art engine starters but which is capable of starting even the largest model airplane engines. Ideally, such a starter would be provided with some sort of support means which would not only secure the starter in a conveniently accessible location without requiring the carrying of substantial additional weight, and which would also allow the modeler to assume a safe position well behind the propeller of the model airplane at all times during the starting operation. Finally, it would be desirable if the engine starter were capable of generating large amounts of torque without the use of a large and heavy 12 volt battery.